Wiki info about Wellington Mk X

A twin-engine medium bomber, the Wellington Mk.X became the last production variant used by RAF Bomber Command. Its design was based on the Mk.III's airframe, and it featured similar armament and equipment. The main difference was a new 1,675 hp Bristol Hercules Mk.VI (though some planes featured the Hercules Mk.XVI) fourteen-cylinder double-row air-cooled engine. There was also a difference less noticeable but no less important than the replaced engine: the switch to newly developed light alloys with a better strength-to-specific gravity ratio. Using this alloy in the aircraft's structure allowed a higher take-off weight while preserving the Mk.III's flight characteristics.
Full-scale production of the Mk.X (Type 448) model started in the autumn of 1942 and it became the most numerous variant of the Wellington, with a combined total of 3,803 aircraft built.
After initial heavy losses in daylight bombing raids at the beginning of the war, the Wellington saw more success after changing role to night bombing. The aircraft also began serving in North Africa in September 1940 and in the Far East in April 1942. By 1942-43, the Wellington became the RAF Bomber Command's primary medium bomber; it was faster than the Armstrong Whitworth Whitley and it had a longer range than the Handley Page Hampden, even though its payload was just as great. In the first "1,000 bomber raid" on Cologne on May 30th 1942, 599 of the 1,043 aircraft were Wellingtons.
The Wellington bombers' last operational sortie with Bomber Command in Western Europe was on the night of October 8, 1943. The Wellington was succeeded by heavy four-engine aircraft such as the Short Stirling, the Handley Page Halifax, and the Avro Lancaster, as the RAF Bomber Command increased its pressure on Germany. However, variants of the Wellington Mk.X continued to serve with RAF Coastal Command for the remainder of the war; the Mks.XI through to XIV were all maritime versions of the Mk.X, fitted with ASV radar. And a variety of armaments. Coastal Command Wellingtons were employed in protecting allied shipping in the South West Approaches from enemy submarines. Notable successes were scored by 172 Squadron, operating from RAF Chivenor, who were the first unit to attack a U-Boat at night using a combination of radar and a special carbon arc searchlight. October 1945 saw the construction of the last of 11,461 Wellingtons, and the aircraft was withdrawn from service in March 1953 after finishing its RAF career as a pilot and navigator trainer.